Optimal design of river nutrient monitoring points based on an export coefficient model

Nutrient concentration is an important factor in identifying the quality of water sources and the likelihood of eutrophication. A nutrient monitoring network is an important information source that provides data on the nutrient pollution status of rivers. Export coefficient models have been widely used to study non-point source pollution. However, there has been little discussion about applying non-point source pollution and export coefficient modeling to design sampling points for monitoring. In this study, a new procedure providing a comprehensive solution was proposed to design nutrient monitoring points, from identifying pollution sources to designing sampling points and frequencies. Application of this procedure to design nutrient monitoring points upstream from the Feitsui reservoirs, Taipei, Taiwan, indicated that agriculture occupied only 7.24% of the area, but it released 45,795 kg/yr, or 41%, of the total nutrient load from non-point sources. Additionally, the optimization conditions defined four sampling points as well as the frequency of sampling at those points in the study area.